The delivery of radio frequency (RF) energy to target regions of tissue is known for a variety of purposes of particular interest to the present invention. For example, U.S. Pat. Nos. 5,868,740, 6,379,353, 6,468,273, 6,889,089, U.S. Patent Application Publication No. 2005-0137659, and PCT application WO 96/29946 describe some of such tissue ablation systems.
The delivery of RF energy to target regions within tissue is used to treat maladies within the body. Thermal coagulation of tissue using RF energy may be delivered to diseased regions, e.g., tumors, for the purpose of ablating predictable volumes of tissue with minimal patient trauma. Physicians frequently make use of tissue piercing probes to gain access to interior regions of the body for this purpose. Such probes may carry an array of elongate (e.g., wire) electrode elements that are deployable from a distal end of the probe into the tissue region to be ablated.
One family of commercially available RF ablation probes are the LeVeen®Needle Electrode and the LeVeen CoAccess™-Electrode System (collectively referred to herein as the “LeVeen ablation probe”), manufactured and distributed by Boston Scientific Corporation. The LeVeen ablation probe comprises an array of elongate wire electrode elements that are deployable from a distal portion of an elongate delivery cannula. A handle is connected to a proximal portion of the delivery cannula, and a plunger is coupled in a reciprocating fashion to the handle. In particular, the plunger is fixedly coupled to the electrode array elements such that, when the plunger is extended proximally relative to the handle, the electrode elements are withdrawn into the cannula, and when the plunger is depressed distally into the handle, the electrode elements are deployed out of the cannula.
Depending on the size of the lesion and the size of the electrode elements needed to ablate the lesion, the attending physician may only deploy a portion of the electrodes to initiate the ablation procedure, and then deploy additional portions (i.e., lengths) of the electrode elements as the procedure continues. However, it may be difficult for the physician to precisely control and deploy the electrode elements using the plunger-handle arrangement. Thus, a need exists for controlling the deployment of elongate electrode elements from probes such as (but not just) the LeVeen ablation probe so the array elements are precisely deployed.